External CSS

im kinda new in html and stuff, but i started some weeks ago with my first site and now i wanted to host it with t35 Hosting. I've my index.html and a style.css, i both uploaded them at t35, but now its like my style.css isnt linked anymore to my index.html, but when i preview them in dreamweaver everythings allright.

I know, its maybe a stupid question, but hey, im still a newb and ive to start somewhere